1. Field of the Invention
The present invention relates to a computer in which a value or a variable (a character) can be input and displayed in the form of a mixed fraction.
2. Description of the Prior Art
FIGS. 14A to 14C show a conventional processing for inputting and displaying a mixed fraction using such a computer. In FIGS. 14A to 14C, a key sequence and a display screen output are shown in the left and right portions, respectively. Each of the symbols A, B, and C represents a value or variable. The symbols A, B, and C respectively denote an integer, the numerator, and the denominator of a mixed fraction.
When a mixed fraction having an integer A and a fraction B/C is to be input, numeric keys or character keys and a mixed fraction key "a b/c" provided on a keyboard are used.
First, the integer A is input and initially displayed at a numerator position, as shown in FIG. 14A. When the mixed fraction key "a b/c" is depressed, the display position of the integer A is moved to an integer portion, as shown in FIG. 14B.
Next, the numerator B is input and displayed at the numerator position, as shown in FIG. 14B. When the mixed fraction key "a b/c" is depressed, the computer goes into a state for waiting an input of the denominator C. A cursor 10 which is shown as a thick underline remains at a denominator position up to this step.
Thereafter, the denominator C is input and displayed at the denominator position, as shown in FIG. 14C. The cursor 10 is moved to the next column on the right side. Thus, a process for inputting and displaying the mixed fraction having the integer A and the fraction B/C is completed.
When an expression in the form of a mixed fraction is displayed, the cursor 10 is moved to a different position, especially from the numerator position to the denominator position in the following manner. The manner is described with reference to FIGS. 15A to 15C.
It is assumed that the underline cursor 10 is positioned at the right end value "6" of the numerator, as shown in FIG. 15A. When a right directional cursor key 11 which is represented by a triangle pointing in the right direction is depressed, the cursor 10 is once moved to a next column on the right side of the right end value "6" of the numerator, as shown in FIG. 15B. At the same time, a borderline 12 between the denominator and the numerator is elongated by a column.
The blank column in the elongated portion of the borderline 12 may be used for inserting or adding a value.
When the right directional cursor key 11 is depressed again without adding a value, the cursor 10 is moved to the left end value "7" of the denominator, as shown in FIG. 15C. At the same time, the elongated portion of the borderline 12 is deleted.
Thus, a process for moving the cursor 10 from the right end of the numerator to the left end of the denominator is completed.
When a value or a variable (a character) is input for the expression in the form of a mixed fraction, the value or variable is input in the order of an integer, a numerator and a denominator, as described above. However, when the integer A is input, the integer A is once displayed at the numerator position and then moved to the integer position, as shown in FIGS. 14A and 14B. Therefore, the conventional processing is likely to cause a misunderstanding or a mistake in the input operation.
In a case where a value or a variable (a character) is input for an expression in the form of an improper fraction or a proper fraction, in order to change the input destination from the numerator to the denominator, a fraction key "b/c" is used instead of the mixed fraction key "a b/c". Conventionally, once an improper fraction or a proper fraction is input using the fraction key "b/c", the fraction cannot be modified by adding or inserting a value or a variable for an integer at the left of the fraction so as to make a mixed fraction.
As described above with reference to FIGS. 15A to 15C, when the cursor 10 is moved on the displayed expression in the form of a mixed fraction, such an unnatural and useless movement or display change that the borderline 12 between the denominator and the numerator is elongated and the cursor 10 is moved to the elongated portion occurs, which causes the operator to be confused.